Electric Drives and Their Control

1. a) Differentiate between active and passive load torques with example? [8]

b) Explain the operation of a closed loop speed control scheme with inner current control loop. [8]

1. a) Suggest the suitable conventions about the signs of torque and speed for multi quadrant operations of drives. Also explain the four quadrant operation in motor? [8]

b) Explain the load equalization in electric drives. [8]

2. a) Explain electric braking of DC separately excited motor with suitable connection diagrams and speed torque curves? [8]

b) What are the power limitations in armature voltage control in DC drives? [8]

2. a) Differentiate between regenerative braking, dynamic braking and plugging. [8]

b) Explain the construction and working of chopper controlled DC drives. [8]

3. a) The useful load torque of 3-phase, 6-pole, 50 Hz induction motor is 162.84 Nm. The rotor emf is observed to make 90 cycles per minute. Calculate: (i) Motor output (ii) Copper loss in motor (iii) Motor input (iv) Efficiency if mechanical torque lost in windage and friction is 20.36 Nm and stator losses are 830W. [8]

b) Explain the stator voltage control for speed control of induction motor. [8]

3. a) Discuss and explain the dynamic braking in induction motor drives. [8]

b) Write a short note on operation of Voltage Source Inverter (VSI). [8]

4. a) Explain using a power circuit, how the speed of an induction motor drive can be controlled by using current source inverter. [8]

b) Explain the slip power recovery scheme with stator scherbius drive in brief. [8]

4. a) Describe the cycloconverter fed induction motor drive. [8]

b) Draw and explain a closed loop operation for a static kramer controlled drive. [8]

5. a) Describe the VSI fed self controlled synchronous motor drive. [8]

b) Explain the control of synchronous motor with current source inverter. [8]

5. a) Explain the braking of synchronous motor with VSI. Draw the speed torque characteristics for regenerative braking. [8]

b) Write a short note on separately controlled synchronous motor drive. [8]